Kallikrein-5, also known as KLK5, belongs to the serine protease family of proteolytic enzymes. The human KLK gene family consists of 15 serine proteases. It is expressed in a variety of tissues including salivary gland, stomach, uterus, lung, thymus, prostate, colon, brain, thyroid, and trachea. The function of the other members of KLK gene family is currently unknown, but evidence suggests that many KLKs are implicated in carcinogenesis.